The alpha9beta1 integrin is expressed in many different tissues, including smooth muscle, epidermis, and neutrophils. Data from alpha9 integrin subunit-knockout mice have implicated this integrin in lymphangiogenesis, thus indicating its potential role in vascular development. In addition, in vitro experiments have shown that the alpha9 integrin subunit can mediate enhanced cell migration in both neutrophils and non-leukocytic cells. In an effort to investigate the molecular mechanisms behind alpha9 integrin-mediated cell migration, spermidine/spermine-N'-acetyltransferase (SSAT), a regulator of cellular polyamine levels, was identified as one alpha9 integrin cytoplasmic domain-binding protein that is specifically crucial for this process. This proposal will investigate how SSAT mediates a9-dependent cell migration. First, to determine if SSAT affects alpha9-specific migration by modulating levels of polyamines inside the cell, transwell migration assays will be performed with cells expressing various mutant SSAT constructs or pharmacologically depleted of polyamines. Next, immunofluorescence and live confocal microscopy of ectopically-expressed fluorescent protein conjugates will be used to determine localization of the alpha9 integrin and SSAT in migrating cells. Finally, the details of the cell migration signal downstream of SSAT-alpha9 integrin interactions will be investigated, using yeast two-hybrid screening to identify other SSAT-binding proteins that are crucial for a9 integrin-mediated migration. The proposed experiments should provide insight into a novel pathway for regulating integrin function.